The slice opening on a headbox in a paper machine defines the thickness of stock that flows out onto the wire. The slice arrangement normally has a fixed slice member and a controlled slice member. A number of jacksrews (for example 50-60) are mounted in a way and distributed in a row across the width of the machine. The jackscrews act against the control lip. By adjustment of the jackscrews the control lip can be changed to adjust the basis weight of the sheet and/or the profile in the cross machine direction. The sheet that is formed and dried in the machine is measured at several points in the cross machine direction. The measurement results can be utilized to adjust the slice screws in corresponding positions, so that the basis weight profile for the stock that flows onto the wire can be optimized, in partiular for cross machine profile control.
The jackscrews are typically only adjustable by hand. Each jackscrew may comprise a simple adjustment screw with very fine threads. Since it is desirable to reduce personnel costs and also to be able to more quickly adjust the slice lip, it is known to equip each jackscrew with a separate reducer (gearbox) and motor that is remotely controlled, whereby the control can be achieved automatically. This may be done, for example with the guidance of the basis weight profile of the dried paper, in order to adjust the profile of the stock layer going onto the wire. In this way the dried paper sheet can be optimized for bone dry weight profile, the moisture profile of the sheet can be leveled, and the drying requirements can be minimized.
Automation of the slice lip adjustment in that manner, however, has several disadvantages. The large number of drive motors and the labor of installing them is costly, and additionally it has been found that the reliability may be degraded. This is because there is a cumulative risk of malfunction that may occur in any one of the large number of drive motors and/or gearboxes, especially in view of the fact that some individual drive motors are only very sporadically energized. An object of this invention is therefore to avoid these named disadvantages by providing an apparatus for control of the jackscrews that adjust the slice opening on a slice on a headbox by acting on the control lip, which apparatus is connected to a remote control arrangement that can itself be controlled in a conventional way.